In recent years, some liquid crystal display devices are equipped with a memory function corresponding to each pixel in order to reduce power consumption. Such a device is called, for example, a “memory liquid crystal display” or simply a “memory liquid crystal”. In general, the memory liquid crystal display is capable of holding one-bit data for each pixel, and performs image display using data held in memory when displaying the same image or an image that barely changes for a long period of time. In the memory liquid crystal display, when once data is written in the memory, the contents of the data written in the memory are held until the next update. Accordingly, little power is consumed during periods other than before and after a change in the contents of an image. As a result, power consumption is reduced compared to liquid crystal display devices without the memory function. Note that driving the liquid crystal using the memory function will be referred to below as “memory drive”.
In conventional memory liquid crystal displays, rectangular pixels are arranged in a matrix in a display portion, as in general active-matrix liquid crystal displays. In addition, as with general active-matrix liquid crystal displays, conventional memory liquid crystal displays include a gate driver (scanning signal line driver circuit) and a source driver (video signal line driver circuit) as driver circuits. In such a configuration, by the operation of the gate driver and the source driver, data corresponding to a display image is stored in memory corresponding to each pixel. Then, the image is displayed on the basis of the data stored in the memory.
Note that in relevance to the present invention, Japanese Laid-Open Patent Publication No. 2007-286237 discloses an invention of a display device including pixel memory circuits configured as shown in FIG. 26. In this display device, one pixel memory circuit is provided for each pixel unit consisting of three, i.e., R, G, and B, subpixels, rather than for each of the R, G, and B subpixels. This inhibits an increase in circuit area and realizes low power consumption owing to drive using memory.